From c0dd239753ab22d059531472b3895669ce44a875 Mon Sep 17 00:00:00 2001
From: Murarth <murarth@gmail.com>
Date: Mon, 16 Mar 2015 13:04:31 -0700
Subject: Add `std::net::lookup_addr` for reverse DNS lookup

Closes #22608
---
 src/libstd/sys/common/net2.rs | 39 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 38 insertions(+), 1 deletion(-)

(limited to 'src/libstd/sys')

diff --git a/src/libstd/sys/common/net2.rs b/src/libstd/sys/common/net2.rs
index e213a86644f..a8ee40639e3 100644
--- a/src/libstd/sys/common/net2.rs
+++ b/src/libstd/sys/common/net2.rs
@@ -10,11 +10,12 @@
 
 use prelude::v1::*;
 
-use ffi::CString;
+use ffi::{CStr, CString};
 use io::{self, Error, ErrorKind};
 use libc::{self, c_int, c_char, c_void, socklen_t};
 use mem;
 use net::{SocketAddr, Shutdown, IpAddr};
+use str::from_utf8;
 use sys::c;
 use sys::net::{cvt, cvt_r, cvt_gai, Socket, init, wrlen_t};
 use sys_common::{AsInner, FromInner, IntoInner};
@@ -126,6 +127,42 @@ pub fn lookup_host(host: &str) -> io::Result<LookupHost> {
     }
 }
 
+////////////////////////////////////////////////////////////////////////////////
+// lookup_addr
+////////////////////////////////////////////////////////////////////////////////
+
+extern "system" {
+    fn getnameinfo(sa: *const libc::sockaddr, salen: socklen_t,
+                   host: *mut c_char, hostlen: libc::size_t,
+                   serv: *mut c_char, servlen: libc::size_t,
+                   flags: c_int) -> c_int;
+}
+
+const NI_MAXHOST: usize = 1025;
+
+pub fn lookup_addr(addr: &IpAddr) -> io::Result<String> {
+    init();
+
+    let saddr = SocketAddr::new(*addr, 0);
+    let (inner, len) = saddr.into_inner();
+    let mut hostbuf = [0 as c_char; NI_MAXHOST];
+
+    let data = unsafe {
+        try!(cvt_gai(getnameinfo(inner, len,
+                                 hostbuf.as_mut_ptr(), NI_MAXHOST as libc::size_t,
+                                 0 as *mut _, 0, 0)));
+
+        CStr::from_ptr(hostbuf.as_ptr())
+    };
+
+    match from_utf8(data.to_bytes()) {
+        Ok(name) => Ok(name.to_string()),
+        Err(_) => Err(io::Error::new(io::ErrorKind::Other,
+                                     "failed to lookup address information",
+                                     Some("invalid host name".to_string())))
+    }
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // TCP streams
 ////////////////////////////////////////////////////////////////////////////////
-- 
cgit 1.4.1-3-g733a5